3x(2x+8)=126

Solution for 3x(2x+8)=126 equation:

3x(2x+8)=126

We move all terms to the left:

3x(2x+8)-(126)=0

We multiply parentheses

6x^2+24x-126=0

a = 6; b = 24; c = -126;
Δ = b2-4ac
Δ = 242-4·6·(-126)
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(24)-60}{2*6}=\frac{-84}{12}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(24)+60}{2*6}=\frac{36}{12}
=3
$